The present invention concerns a programmable digital measuring and control instrument adapted to display numerical values coming from analog to digital conversion of electric signals in form of numeric data.
Electronic metering devices or apparatuses, both analog and digital, provide a more or less accurate measurement of a selected quantity (e.g. Volt, Ampere, etc.) relating to an electric signal. Therefore, the use of such electronic metering devices for measuring physical quantities of a kind different from the electric one (e.g. a pressure) requires the interposing of a suitable transducer adapted to convert into an electric signal a given physical quantity.
It is evident from the above that when the electric signal is a non-linear function of the physical quantity under consideration, the information supplied by such instruments is not easy to be interpreted, unless a proper conversion is carried out by means of known tables.
For a better understanding of the above FIG. 1 shows, as an example, the characteristic curve of the electric signal generated by a transduction device as a function of the residual inner pressure within a housing, e.g. a ion pump used as a vacuum gage or vacuometer, representing the quantity to be measured. As it is easily noted, the current values vary in a non-linear manner with respect to the pressure and the knowledge of such values is an indirect measurement which is of little use for an operator needing as a matter of fact a direct display of the pressure value.
Anyhow, while in an analog instrument it is possible to overcome such drawback by means of suitable dials printed with non-linear scales and having scale graduations directly reading the values of the quantity being considered instead of that of the electric signal actually measured by the instrument, this is not possible for instruments of digital type.
The present invention aims to provide a programmable digital measuring instrument wherein the level of the input electric signal can be displayed by means of digit, letters or both, programmable as desired, and therefore is capable to be programmed in such a way as to display data that varies in a linear manner even when the input signal varies in a non-linear manner with respect to the quantity to be measured.
A further object of the invention is that of providing a digital and programmable measuring instrument able to store several series of data corresponding to different scales for a same input signal so as to provide for a wider use of the instrument over a longer period of time.